In solid state lighting applications such as those that utilize light emitting diodes (LEDs), it is important to have high brightness output and consistent light output performance over a long period of time. An LED package may be provided with anode and cathode connections that place the LED die in communication with an electrical circuit for supplying a bias voltage to the LED die. An LED package may also include phosphors to produce a white light emitting source using a colored LED die. The LED die may be positioned within a cup-shaped cavity of a housing in order to provide an initial focus for light output from the LED die. In order to increase light output from the LED device, the cavity may have reflective sidewalls. For example, with a housing manufactured from a plastic material such as polyphthalamide (PPA), the reflective sidewalls may be white.
Along with light output, LED devices also generate heat. Junction temperature refers to the highest temperature generated by the LED device, which typically occurs at the junction between the LED device and the substrate on which it is mounted. High junction temperatures can quickly degrade a plastic housing and cause white reflective sidewalls to turn yellow, thereby reducing their reflectivity and decreasing the light output of the LED package.